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KMID : 1094720090140040457
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Biotechnology and Bioprocess Engineering
2009 Volume.14 No. 4 p.457 ~ p.466
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Extracellular β-glucosidase Production by a Marine Aspergillus sydowii BTMFS 55 under Solid State Fermentation Using Statistical Experimental Design
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Madhu K. M.
Beena P. S.
Chandrasekaran M.
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Abstract
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A potential fungal strain producing extracellular β-glucosidase enzyme was isolated from sea water and identified as Aspergillus sydowii BTMFS 55 by a molecular approach based on 28S rDNA sequence homology which showed 93% identity with already reported sequences of Aspergillus sydowii in the GenBank. A sequential optimization strategy was used to enhance the production of b-glucosidase under solid state fermentation (SSF) with wheat bran (WB) as the growth medium. The two-level Plackett-Burman (PB) design was implemented to screen medium components that influence β-glucosidase production and among the 11 variables, moisture content, inoculums, and peptone were identified as the most significant factors for β-glucosidase production. The enzyme was purified by (NH4)2SO4 precipitation followed by ion exchange chromatography on DEAE sepharose. The enzyme was a monomeric protein with a molecular weight of ~95 kDa as determined by SDS-PAGE. It was optimally active at pH 5.0 and 50°C. It showed high affinity towards pNPG and enzyme has a Km and Vmax of 0.67 mM and 83.3 U/mL, respectively. The enzyme was tolerant to glucose inhibition with a Ki of 17 mM. Low concentration of alcohols (10%), especially ethanol, could activate the enzyme. A considerable level of ethanol could produce from wheat bran and rice straw after 48 and 24 h, respectively, with the help of Saccharomyces cerevisiae in presence of cellulase and the purified β-glucosidase of Aspergillus sydowii BTMFS 55.
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KEYWORD
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Aspergillus sydowii, β-glucosidase, Plackett-Burman, SSF, wheat bran
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